Structural and Spectroscopic Characterization of Monolayers of Mn12 Single Molecule Magnets

Abstract

In the course of this thesis, the possibility to deposit intact Mn12 single molecule magnets on conductive surfaces has been investigated which is required for a potential application of this class of molecules in future spintronic devices. A comparison of a variety of established or newly developed preparation methods indicates that many of the previous results on Mn12 monolayers may have to be reassessed. On the other hand, a fully reproducible deposition technique based on a ligand exchange reaction was developed. Many of the experimental techniques commonly used for the characterization of Mn12 monolayers, like scanning probe techniques, photoelectron spectroscopy, and synchrotron-based spectroscopic measurements have been investigated with respect to their suitability for a profound corroboration of the integrity of the molecules. The results demonstrate that none of the previously applied investigation techniques is capable of unambiguously clarifying the ability to obtain monolayers of intact Mn12 molecules. In particular, X-ray based investigation techniques were found to be inappropriate for studies on Mn12 monolayers. Nevertheless, the comparison of all results provides strong indications that the structural integrity of Mn12 molecules deposited via a ligand exchange reaction can be preserved. Advanced scanning tunneling spectroscopy modes were used to derive electronic as well as geometric properties of individual Mn12 molecules. The perfect agreement with theoretical calculations and consistent chemical properties substantiate the integrity of the molecules. The results obtained in this thesis lay the foundation for a variety of future magnetic field dependent cryogenic scanning tunneling spectroscopy measurements on Mn12 molecules and also provide novel concepts for the study of individual single molecule magnets in general.